Mike Gerwitz

Activist for User Freedom

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-rw-r--r--src/coreutils/cat.sh97
1 files changed, 97 insertions, 0 deletions
diff --git a/src/coreutils/cat.sh b/src/coreutils/cat.sh
new file mode 100644
index 0000000..52c3a93
--- /dev/null
+++ b/src/coreutils/cat.sh
@@ -0,0 +1,97 @@
+#!/bin/bash
+# Bash alternative to external cat call
+#
+# Copyright (C) 2014 Mike Gerwitz
+#
+# This file is part of pkgsh.
+#
+# pkgsh is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+# N.B. While this shell implementation may be faster for most use cases, the
+# external binary will likely be much faster for large streams.
+#
+# This also contains some convenience functions that are not part of
+# GNU coreutils.
+##
+
+[ -z $__PKGSH_INC_COREUTILS_CAT ] || return
+__PKGSH_INC_COREUTILS_CAT=1
+
+
+##
+# Echo characters from stdin up to (but not including) the provided
+# delimiter
+cat-until()
+{
+ local -r delim="${1?Missing terminating delimiter}"
+ local -r file="${2:-/dev/stdin}"
+
+ read -rd "$delim" < "$file"
+ local -ri result=$?
+
+ echo -n "$REPLY"
+ return $result
+}
+
+
+##
+# Echo characters from stdin up to and including the provided delimiter
+cat-until-incl()
+{
+ # `cat-until` will validate
+ local -r delim="$1"
+ cat-until "$@" \
+ && echo -n "$delim"
+}
+
+
+##
+# Proxies to either the shell implementation of cat or the system binary,
+# depending on support
+cat()
+{
+ [[ "$1" =~ ^-[^-\ ] ]] \
+ && command cat "$@" \
+ || quickcat "$@"
+}
+
+
+##
+# Limited implementation of `cat` for performance
+#
+# TODO: The proper research has not yet gone into optimizing this; this is
+# just an initial implementation to get things going. I will be addressing
+# this shortly.
+#
+# TODO: Exit status.
+quickcat()
+{
+ local in="${1:-/dev/stdin}"
+ [ "$in" == - ] && in=/dev/stdin
+ readonly in
+
+ while true; do
+ IFS= read -r || {
+ echo -n "$REPLY"
+ break
+ }
+
+ echo "$REPLY"
+ done < "$in"
+
+ if shift && [ $# -ne 0 ]; then
+ quickcat "$@"
+ fi
+}
+